Valves and the like used in the petroleum and chemical industry commonly are used to control the flow of hazardous and toxic chemicals. Since the chemicals that these valves contain can be dangerous, it is important that leakage or emissions from around the valve stems be prevented and the valve stems be continually monitored.
Engineers from the petroleum and chemical process industry, along with representatives from the EPA, have worked jointly to develop design guidelines for seals to control such emissions. One such guideline requires the use of dual mechanical seals with a pressurized non-volatile benign barrier fluid between the seals. The pressure of the barrier fluid is regulated to ensure a correct pressure range relative to the process fluid pressure to prevent leakage to the external environment, and the system is monitored to detect leakage from the seals.
U.S. Pat. Nos. 5,746,435 and 5,906,374 have been granted to the inventor herein disclosing a dual seal barrier fluid leakage control apparatus employing a pressure intensifier and other components carrying out operations that address these problems. However, a drawback of this control apparatus is that, for certain operating conditions, it is too costly and large in size to be a practical solution. It also provides only an electronic measurement of the volume of barrier fluid.
Consequently, there is a continuing need for further innovations that will overcome these drawbacks.